1. Field of the Invention
The present invention relates to a combined thin film magnetic head provided with a magnetoresistive reproducing head part and an inductive recording head part, and particularly to a method for fabricating such a magnetic head.
2. Description of Related Art
A magnetoresistive element is an element which has a high sensitivity sufficient to precisely detect changes in an external magnetic field through the magnetic resistance changes therein. In view of such a nature, efforts have been made to investigate its application to a reproducing magnetic head for reading information stored in a magnetic recording medium such as a hard disk. However, such a magnetoresistive element is solely applicable to the reproducing head. Accordingly, other efforts have been made to investigate a recording/reproducing magnetic head applicable to hard disks, i.e. a combined thin film magnetic head which combines a reproducing head comprising the magnetoresistive element with a recording head comprising an inductive thin film magnetic head.
Such a combined thin film magnetic head is generally constructed by forming a magnetoresistive reproducing head part on a substrate and thereafter forming an inductive recording head part thereon. The magnetoresistive reproducing head part is magnetically shielded by upper and lower shielding layers. The inductive recording head part has upper and lower core layers which extend in parallel to pass centrally through a coil formed of a thin film. One end of the upper core layer is connected to a corresponding end of the lower core layer. Another end of the upper core layer is spaced from a corresponding end of the lower core layer to define therebetween a gap for constituting a detection region. In general, the combined thin film magnetic head incorporates a single magnetic layer for constituting the upper shielding layer for the reproducing head part as well as the lower core layer for the recording head part, i.e., the single magnetic layer serves as the shielding layer and also as the lower core layer. Such a magnetic layer serving as the shielding layer and also as the lower core layer is referred to as a "merged core" throughout the specification of the present application.
A track width in the reproducing head part is generally specified by a distance between electrodes for passing a detection current through the magnetoresistive element. On the other hand, a track width in the recording head part is specified by a length of a gap defined between distal ends respectively of the merged core and upper core layers, and generally by the localized provision of the upper core layer. Accordingly, subsequent to deposition of the upper core layer over an entire surface of an underlying layer, the upper core layer portion deposited outside the localized region must be completely removed such as by etching, that is, the etching needs to reach completely to a surface of a gap layer defined between the merged core layer and the upper core layer to remove the upper core layer from the region outside the localized region. Since the film thickness of the gap layer is very small, it has been necessary to carry out successive partial etching steps for etching the merged core layer, serving as the lower core layer. Intentionally etching an upper portion of the merged core layer to a width equal to the gap length has been also suggested to control a magnetic field to be produced in the gap.
However, etching the merged core layer, if over only partly, undesirably impairs its function as the upper shielding layer. Furthermore, the recent demand for higher magnetic density recording requires a smaller gap length, and accordingly a narrower track width. It is therefore desired to provide a method wherein the track width can be defined with precision by the selective etching which stops at the gap layer and leaves the merged core layer unetched.